This invention relates to a one way gate, for items traveling along a transport path including a transport surface against which items are supported during travel. Such transport paths are commonly employed in, e.g., postage meters and other mailpiece handling apparatuses.
One problem encountered-from time to time in postage meters is that of so-called "false tripping". When a mailpiece (e.g. an envelope) is inserted into the transport path of a postage meter for franking, a mechanical or optical system detects the presence of the mailpiece and initiates rotation of the print drum of the postage meter to frank the mail or a label to be adhered to the mailpiece during operation of the machine. The mailpiece is advanced to its franking position by means of e.g. a drive roller that drives it along the transport path formed by the deck of the postage meter.
Occasionally, the drive roller fails to engage the mailpiece correctly. This may occur e.g. when the mailpiece is damaged or slippery. Usually, such imperfect gripping of the mailpiece only results in a slight delay in the mailpiece being fed to its franking position, but there is a tendency for operators of postage meters to try and pull the mailpiece backwards along the transport path to remove it from the postage meter if it is suspected that imperfect gripping of the mailpiece has occurred. When operators try and withdraw mailpieces in this way, false tripping frequently results, i.e. the postage meter print drum rotates as though a mailpiece is present, despite the absence of the mailpiece. This is a particular problem in comparatively simple postage meters lacking means for automatically verifying that the mailpiece is in the correct position for franking.
Since postage meter users pay for all postage registered by the meter regardless of whether every such registration results in the franking of a mailpiece, and since false tripping results in the decrementing of the descending register of the postage meter despite no mailpiece having been franked, it is clearly desirable to provide a means whereby the incidence of false tripping is reduced or even eliminated.